Recipient intramuscular administration of naked plasmid TGF-β1 attenuates lung graft reperfusion injury

Background: Gene therapy may be an effective strategy for modulating lung graft ischemia-reperfusion injury. We investigated whether recipient intramuscular (IM) naked plasmid gene transfer of transforming growth factor β1-active (TGF-β1-active) ameliorates lung graft ischemia-reperfusion injury. Methods: Preliminary studies in F344 rats demonstrated that gastrocnemius muscle transfection of TGF-β1-active produced muscle and plasma protein expression at 24 and 48 hours after transfection. Recipients (n = 8) received IM injection of naked plasmid-encoding chloramphenicol acetyl transferase (CAT), TGF-β1-latent or TGF-β1-active, respectively, at 24 or at 48 hours before left lung transplantation. We did not treat the control group before transplantation (18-hour cold ischemia). Donor lungs were flushed with low-potassium dextran-1% glucose and stored for 18 hours at 4°C. All groups were killed at 24 hours after transplantation. Immediately before killing the animals, we clamped the contralateral right hilum and assessed graft function. We measured wet-to-dry ratio (W/D), myeloperoxidase, pro-inflammatory cytokines (interleukin 1 [IL-1], tumor necrosis factor α [TNF-α], interferon-γ [INF-γ], and IL-2) and performed immunohistochemistry. Results: Arterial oxygenation was greatest in the recipient group transfected with TGF-β1-active at 24 hours before transplantation compared with CAT, TGF-β1-latent, and 18-hour cold ischemia groups (p < 0.01). The W/D ratio and myeloperoxidase decreased in both 24- and 48-hour groups, with TGF-β1-active compared with CAT, and 18-hour cold ischemia groups (W/D, p < 0.02 and p < 0.004, respectively; myeloperoxidase, p < 0.05 and p < 0.01, respectively). All pro-inflammatory cytokines decreased in the 24-hour TGF-β1-active group compared with CAT, TGF-β1-latent, 18-hour and 1-hour cold ischemia, and non-treated lung groups (IL-1β, p < 0.03; TNF-α, p < 0.02; IFN-γ, p < 0.001; IL-2, p < 0.0001). In 24- and 48-hour groups with TGF-β1-active, immunohistochemistry showed marked staining of Type I and Type II alveolar cells and of macrophages from the apical to the caudal sections of the lung grafts. Conclusions: Recipient IM administration of naked plasmid encoding TGF-β1-active before transplantation ameliorates lung isograft reperfusion injury after prolonged ischemia.